Thanks for the PR! One immediate things is jumping out here:

len() counts bytes and not runes, which are not always the same. Similarly, some runes occupy two cells. For example:

// 3 bytes, 3 cells
Hi!

// 7 bytes, 5 cells:
世界!

So, in short, keep in mind that horizontal scrolling will need to handle double-width runes. Here’s a more in-depth example that breaks it down further:

https://go.dev/play/p/7lPoU2SMjn5

Thanks for the PR! One immediate things is jumping out here:

len() counts bytes and not runes, which are not always the same. Similarly, some runes occupy two cells. For example:

// 3 bytes, 3 cells
Hi!

// 7 bytes, 5 cells:
世界!

So, in short, keep in mind that horizontal scrolling will need to handle double-width runes. Here’s a more in-depth example that breaks it down further:

https://go.dev/play/p/7lPoU2SMjn5

It's a good point. I guess I have to use lipgloss.Width here.

Waiting for this PR merge and tagging.
Will continue after that.

Don't merge it yet, please.
I'm gonna write some simple tests later this evening.

Done!
@meowgorithm could you check it, please?
I can suppose that last test case (list: with y offset: horizontal scroll) can be too complicated. But I'm not sure it it's better to change it.
WDYT?

Thanks, @tty2. Before we get to this, do you mind adding some tests with double-width runes? That is going to be the number one thing we'll want to verify. In particular, cases where there's a mix of single and double width runes.

These tests I've written inside go-runewidth library. For TruncateLeft function I use here.
But ok I'll write them here as well. I'll do it tomorrow.

@meowgorithm
Done! Check the last test case.

Hi, @meowgorithm
Should I change anything?

Hey, @tty2! Thanks for all your work on this so far. It's going to be a little bit of time until we can give this a proper review, but I promise we'll get to it.

We'd absolutely love this functionality as well!

However, I tested this branch and found a potential issue: the rune trimming also trims color codes. The below are a series of screens showing horizontal scroll of a terraform plan that includes colored text:

It would be great to have this feature as well.

@Caden64
Hey
Thanks for your ping via email. Sorry I haven't looked at this PR for years.
Thanks for providing your patch, it helped a lot but I used TuncateLeft that was implemented after, cause it was exactly we need here. I believe @caarlos0 mentioned it for help.
Hopefully it is what we need now.
Could you review it please?

thanks @tty2!

I'll look into glamour and what's needed there, just to make sure we're not missing anything here. :)

• models in here should support this feature, such as table

Hi @caarlos0
I fixed tests for viewport only yesterday.
I see you are going to look into other part of the lib.
Sorry, it's hard to recall everything after 2 years delay, but I'm sure that there was some flag before for the behavior you implemented here #240 (comment) .
And as I understand these changes break tests in table too.
I'm confused now.
In the initial issue #235 you can find that there was the way to prevent wrapping onto a new line (see screenshots).

this change is not breaking the other models in the lib, for instance table, i guess.

a proper keymap and update implements are required to do this feature for them and this could be in another PR

cannot wait this til next two years 😇 @meowgorithm @bashbunni are you mind to check this?

I hear you @flavono123. We're all on holiday through the new year but we'll pick this up after then. We've done an initial review internally, made some changes, and we intend to merge this.

thanks got it. have a holy holiday

Alright, so I pushed a few changes to make the horizontal scroll API better match the rest of the API.

I think this is ready to go (the implementation is really good) although I'd love to figure out why it's breaking table tests first.

Will take a look later

Thanks for the PR, @tty2, and for the discourse, @flavono123. This was a long time coming.

We expect to release this soon.

Hi Guys,
can we expect new features like this and #697 to be integrated with v2 alpha releases?

thank you all by all the amazing work btw!

@rdalbuquerque Yep, absolutely. We regularly merge new stuff on master into v2-exp. We plan to tag another v2 prerelease soon.